A polyorganosiloxane composition of a condensation reaction type that cures at room temperature into a rubber-like elastic body is in wide use as an elastic adhesive, a coating material, an electrical insulation sealant, and the like in an electric and electronic industry and also as a building sealant or the like.
Among such room-temperature-curable polyorganosiloxane compositions of the condensation reaction type, that of a single-component type (or single-package type) in which a curing reaction takes place when it comes into contact with moisture in the air is easy to handle because it does not require a troublesome work of weighing and mixing a base polymer and a cross-linking agent, a catalyst, or the like immediately before use. However, since its curing gradually progresses inward from its surface, it has a drawback of slow curing speed and poor deep-part curability.
On the other hand, a room-temperature-curable polyorganosiloxane composition of a two-component type is higher in curing speed and higher in deep-part curability than the single-component type. Generally, this composition is used as a composition of a so-called multi-package-type of which room-temperature-curable base composition and cross-linking composition are separately prepared, are preserved in separate containers, and are mixed immediately before use. The base composition comprises polydiorganosiloxane having termini capped with hydroxyl and/or alkoxyl groups and an inorganic filler. The cross-linking composition comprises a cross-linking agent and a curing catalyst (see, for example, a Patent Reference 1).
However, the conventional room-temperature-curable polyorganosiloxane composition of the two-component type is poor in adhesiveness to various kinds of substrates, and in particular, when the composition is added with zinc carbonate, aluminum hydroxide, or the like to impart flame retardancy, its hardness may increase due to an increase in an amount of a filler, resulting in poorer adhesiveness.
Patent Reference 1: JP-A 2005-105235 (KOKAI)